DISEASE CHARACTERISTICS: Histologically confirmed recurrent or progressive glioblastoma multiforme Previously treated with cytoreductive surgery Unilateral, unifocal tumor with a volume of 5-80 mL Not eligible for further radiotherapy due to prior external beam radiotherapy No multifocal, brain stem, or infratentorial tumor or tumor invading midline No tumor with a clinically significant mass effect (greater than 5 mm midline shift) while on stable dose of corticosteroid No clinical symptoms attributed to uncontrolled increased intracranial pressure and/or edema of the brain